End stage renal disease (ESRD) is a debilitating disorder characterized by the steady decline of kidney function. Healthy kidneys not only clean the blood by filtering out extra water and wastes, but they also produce hormones that maintain strong bones and healthy blood. When the kidneys fail, numerous debilitating effects are experienced, including rising blood pressure, accumulation of fluids and toxic wastes in the body and insufficient red blood cell production. Treatment is therefore required to replace the work of the failed kidneys.
Due to the lack of donor organs and high rate of rejection in kidney transplantation procedures, the majority of ESRD patients rely on one of two dialysis therapies to replace kidney function. The most common treatment is hemodialysis, is a procedure that uses a machine and an artificial kidney to remove toxins and water from a patient's blood. Hemodialysis requires a special filter called a dialyzer to clean the blood. During treatment, blood travels through tubes into the dialyzer, which then filters out waste and extra fluids. The newly cleaned blood flows through another set of tubes and back into the body. Hemodialysis patients typically travel to a dialysis clinic three times per week for 3-4 hours per session.
Peritoneal dialysis is a second procedure that replaces the work of the kidneys. This procedure removes toxins and water through the patient's peritoneal membrane, a large membrane surrounding the organs below the diaphragm. Almost always performed at home, fluids can be exchanged manually four or five times daily or automatically overnight. A cleansing solution, called dialysate, travels through a special tube into the abdomen. Before peritoneal dialysis can be performed, a minor operation is required to insert a soft, plastic tube into the abdomen. A few inches of the tube, or catheter, remains outside the abdomen, but can be hidden by clothing. The catheter is used to connect the patient to bags of dialysate. Fluid, wastes and chemicals pass from tiny blood vessels in the peritoneal membrane into the dialysate. After several hours, the dialysate gets drained from the abdomen, taking the wastes from the blood with it. The abdomen is then filled with clean dialysate and the cleansing process begins again. Peritoneal dialysis is a very time consuming and tedious exchange process, wherein patients experience frequent infections such as peritonitis.
Each of these procedures presents high risks of injury causing loss of vascular access, such as thrombosis, infection, disconnection and hemorrhage. In addition, there are increased risks of fluid volume deficits which may be related to excessive fluid losses, shifts via ultrafiltration, hemorrhage from altered coagulation, disconnection of shunts and fluid restrictions.
Furthermore, studies of patients who require frequent dialysis indicate that numerous treatments of shorter duration can significantly improve clinical outcomes, reduce total treatment costs and improve the quality of life for dialysis patients. It has been proven that the most efficient cleansing of the blood takes place during the first one to two hours of a dialysis session. Increasing the length of time of dialysis is, therefore, not the most efficient way to improve the dose of dialysis. (Source: “Treating End Stage Renal Disease: The Health and Business Case for Daily Dialysis”, www.aksys.com, 1999).
Before the initial treatment, access to the bloodstream must be established. The access provides a way for blood to be carried from the body to the dialysis machine and then back into the body. Thus, prior to establishing dialysis treatment, a minor operation is often performed to subcutaneously implant a port in the patient. Ports are totally implantable vascular access devices that permit the infusion of medications, nutrients, blood products and other fluids. Typically, the port includes a chamber and an access region where the chamber is attached to an implanted fluid flow conduit, such as a catheter. The conduit is, in turn, secured to a blood vessel. In the case of veins, the conduit is typically indwelling and in the case of arteries, the conduit may be attached by conventional anastomosis.
Needles and other access tubes may be percutaneously attached to an implanted port in several ways. Conventional blood access designs use an entry needle to force open a gating mechanism leading to a fluid flow conduit in fluid communication with a subcutaneous port. These designs are not always airtight and often require additional mechanisms so that a heparin lock may be established between treatment sessions. Furthermore, any entry or activation needle must be secured within the port body throughout the procedure, providing an opportunity for the needle to withdraw during the dialysis procedure. Numerous attempts have been made to provide dialysis access devices which overcome the above described problems. Examples of such devices are described in U.S. Pat. No. 3,998,222 to Shihata which discloses a subcutaneous shunt having an axially and rotatably movable valve therein; and U.S. Pat. No. 4,092,983 to Slivenko which discloses a blood access device wherein a pair of tubular conduits is provided on a generally cylindrical housing. Other systems that are currently marketed as solutions to the vascular access dilemma include a dual-access port and catheter access system known as Dialock (a registered trademark of Biolink of Middleboro, Mass.) and an implantable valve and cannula system known as LifeSite (a trademark of Vasca, Inc. of Tewksbury, Mass.).
The number of ESRD patients worldwide requiring dialysis is growing at a significant rate. This growth is primarily attributable to an aging population and the increasing life expectancy of patients with a high risk of ESRD. Yet, even in view of the increasing need for more frequent vascular access and the growing numbers of patients requiring such treatment, none of the above described devices provides the critical combination of (1) a needle that establishes and maintains heightened efficiency of blood flow so as to reduce the discomfort experienced by the patient and (2) a subcutaneous device actuatable by the needle that not only assists the needle with such efficiency, but also prevents inadvertent needle withdrawal. Furthermore, such devices do not address the need to control needle bevel orientation, which is critical to maximizing blood flow rates and the overall efficiency of the dialysis procedure. If the bevel opening faces a wall or is obstructed in any way, flow will be adversely affected, thereby lengthening and complicating the dialysis procedure.
It is therefore desirable to provide a system which obviates the above mentioned problems while reducing the number of components required to effect successful dialysis and other fluid transfer procedures. Such a system would provide an implantable port which only permits fluid flow upon establishment of fluid communication between an engagement member and a fluid flow conduit, such fluid communication being selectively established by mating of the engagement member with the dialysis port.